Superconducting instability in the infinite-U Anderson lattice in the presence of crystal electric fields

Abstract

We have studied the mean-field quasiparticle states and quasiparticle interactions in the infinite-U Anderson lattice in the presence of crystal electric field of cubic symmetry. We assume a lattice of 4f sites, each with a total angular momentum of J=5/2 that is split into a low-lying doublet of Γ7 symmetry and an excited quartet of Γ8 symmetry. Slave bosons on the 4f sites create and destroy 4f0 configurations and Lagrange multipliers at each 4f site enforce the occupancy constraint due to the infinite Coulomb repulsion. The quasiparticle states are strongly peaked at the points where the Fermi surface intersects the axes of the cubic Brillouin zone, leading to what we call ‘‘hot spots.’’ We have calculated the effective magnetic moment and the Wilson ratio for these anisotropic quasiparticle states. Quasiparticle interactions are due to exchange of 4f density fluctuations. We use the analytic tetrahedron method to calculate the dressed (to order 1/N) boson Green functions. In weak coupling, the exchange of the dressed bosons gives rise to a superconducting instability of T1g, xy(x2-y2), symmetry. The A1g, ‘‘s-wave,’’ channel has strongly repulsive interactions and hence no pairing instability. The T2g channel exhibits weakly repulsive interactions. Average quasiparticle interactions in the Eg, x2-y2, 3z2-r2, channel fluctuate strongly as a function of the number of tetrahedra used to calculate the bosonic Green functions, lending only weak evidence for an instability of Eg symmetry.

Source-reported materials — not catalogue approval

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